This invention relates to coking in general and, in particular, to a new and useful apparatus and method for clarifying coke quenching water or other waters contaminated by solids with a wide grain spectrum, where suspended and entrained fine portions of solids are removed from the water by filtration and the clarified water is returned in a cycle.
A method for clarifying coke quenching water is known from German Pat. No. 858,393, in which the contaminated coke quenching water is conducted by fall into a basin and, while rising slowly in the basin, through a filter. The filter may contain lump coke as a filtering material, and must be replaced constantly corresponding to the load.
In arrangements for carrying out the method, a horizontal filter is arranged, for example, in a basin above the outlet of the downpipe of the coke quenching water supply. A downpipe passing through the filter is arranged in the basin for the supply of the contaminated coke quenching water and the receiving end of a bucket conveyor is arranged in the bottom part of the basin and rises outside of the basin. A water discharge is arranged in the upper part of the basin and it has a receiving end which is lower than the upper end of the downpipe. A tank which is placed in the basin has walls which in part form the boundary walls of the basin. A closable water supply for fresh water is located above the filter and a closable water discharge is arranged below the filter.
The realization of this method, as well as the other preparation methods requires large settling basins. Since, in recent years, space has become extremely scarce, particularly for coking plants, in order to save space, space-saving designs of the accessory coking plants are being utilized, whenever possible, since, in many cases, expansion of the coking plant is not possible.
Due to the general increase of the coal and coke throughput in heavy duty coking batteries, the settling basins must become increasingly larger in volume in order to ensure sufficient clarification with increasing amounts of water for the quenching operation.
The operation of the presently known plants also raises problems in other sectors. Thus, the engineering effort for emptying the settling basins by means of shovel dredgers in considerable. In addition, the regular dredging of the settling basins has an adverse effect on the clarification because it causes disturbances in the basins. Measurements have shown that the amounts of dross sucked in by the quenching water pump during the removal of the dross, and also for hours thereafter are up to five times greater than normal. Since there is a direct relationship between these suspended and entrained quantities and the emission of coke dust from the quenching tower, more dust is correspondingly emitted from the quenching tower during this time also.
The object of the present invention, therefore, is to provide a method for clarifying excess coke quenching water and other contaminated waters, in which a large settling basin is not required, the engineering effort for the clarification of the water is reduced, clarification result is improved and the emission of solids during the quenching is decreased.
For the solution of this problem, the invention suggests a method of the above-defined type where the substances removed from the contaminated water themselves form a filter bed, and the water flows, at first, through such a filter from the top to the bottom. The preclarified water is then refiltered in a trough basin rising from the bottom to the top and is then conducted into a discharge channel where the filter, traversed from top to the bottom, is broken down by mechanical means on the underside to the extent at which it is built up on the surface, by the solids arriving with the water.
The water which is filtered from the top to the bottom flows directly after leaving the first filter into a trough basin designed as a calm region, in which, according to the invention, it rises at a lower speed than it sinks in the inner filter.
The direction of flow and the uniform distribution of the water over the entire cross-section can be controlled in the trough basin, according to the invention, so that one or more vertically adjustable partitions are provided in the trough basin.
In order to prevent flying ashes from the coking plant and very fine suspended matter in the quenching water from getting into the clarified water where the filter has disturbances, it is advisable for the water to pass through a replaceable screen and/or a second filter of lump coke, nut coke, coke dust or other regenerable material, such as gravel, preferably, from the bottom to the top, before it enters the discharge channel.
A particularly suitable arrangement for carrying out the method, according to the invention, consists of a filter shaft, which is open at the top and has vertical walls or walls offset at the bottom, and includes an upper storage chamber for the water, which is intermittently introduced.
The contaminated quenching water is fed to the first filter over a channel with adjustable outlet openings which ensure a uniform distribution of the water over the entire filter surface, so that the material of the filter slides by itself into or onto the discharge device, one or several of which are connected with the bottoms. Between the inclined bottoms and the bottom edge of the filter shaft walls, there is a sufficiently large interval that the water issuing from the inner filter shaft can flow at a lower speed into the outer trough basin than that which corresponds to the sinking speed in the upper part of the coke filter.
In a preferred embodiment of the invention, frame-type, vertically adjustable nested partitions, acting as straightening blades, are arranged in the trough basin around the inner filter shaft in those areas where the filtered water rises. Both the upper overflow edge and the bottom edge of the partitions are arranged slightly lower from wall to wall and from the inside to the outside. The resistances to the water issuing from the coke dust, which vary over the surface of the filter arrangement, can thus be compensated so that the entire surface of the trough is optimally utilized by the uniform rising speed of the water.
In the method according to the invention, the first filter is renewed so that the height portion of the filter built up at the top by the arriving coke dust is mechanically broken down on the underside is exactly the same amount. The removal of the filter material can be effected by known conveyor and branching means, one or several conveyor screws, bucket conveyors, multicell belts, chain conveyors, broaching plows, etc.
To ensure a constant filter thickness, it is advantageous if the conveyor devices remove the filter material automatically, controlled by filling level monitors. If necessary, two such coke filter plants can be arranged side-by-side or in tandem, and they may be operated alternately. In general, however, one of these plants will be sufficient.
Tests on arrangements, according to the invention, have shown surprisingly that the liberation of the quenching water of solids contained therein is substantially improved by this type of filtration, compared to the conventional plants. Since a part of the solids contained in the quenching water gets into the atmosphere during the quenching of the coke by the lift of the steam, a reduction of the solid content in the quenching water leads, at the same time, to a reduction of the dust emissions during the quenching of the coke, which helps to reduce environment pollution. Furthermore, a small amount of coke dust in the quenching water leads to less wear of the pump and pipe line system. An additional advantage of the invention is the relatively small dimensions of the arrangement, so that it is also possible to install it in existing settling basins, and the technical expenditures are greatly reduced overall.
The method also has an advantageous effect on an important quality feature, the so-called M10 value, and on the appearance of the coke which is produced thereby, because the solids quenched again in the quenching water cycle and not deposited there are transferred to the coke, thus imparting the known dark color to the coke. On the other hand, the invention produces a coke with the desired silver-grey appearance.
Accordingly, an object of the present invention is to provide a method for clarifying coke quenching water or other waters contaminated by solids with a wide grain spectrum, where the fine portions of solids suspended and carried along in the water are removed from it by filtration, and the clarified water is returned in a cycle, comprising, depositing the water into a filter shaft so that the substances removed from the contaminated water themselves form the filter bed in the shaft, continuing to pass the water through the filter bed from the top to the bottom in a manner so that the velocity of water flow in the filter bed decreases constantly and the water which passes therethrough is preclarified, subsequently refiltering the preclarified water in a trough basin which rises from the bottom to the top, directing the refiltered water into a discharge channel, and breaking down the filter bed on its underside to the same extent as it is being built up by the direction of the quench water with the solids therein into the filter shaft.
A further object of the invention is to provide an apparatus for clarifying coke quenching water and similar water-containing solids, which comprises, a storage container which has a downwardly narrowing top portion and a downwardly widening bottom portion beneath said top portion with a feed channel disposed above the top portion having a discharge for discharging the quenching water into the top portion so that it accumulates in a filter shaft formed by the bottom and top portions and flows upwardly and through a trough basin surrounding the top portion so that the prefiltered water is refiltered, the filter shaft having a bottom discharge with means for carrying away a portion of a bottom of the bed which is equivalent to the amount being built up by the discharge of the water-containing solids therein.
Another object of the invention is to provide an apparatus for clarifying coke quenching water which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.